1. Field of the Invention
The present invention relates in general to systems for cooling electronic components mounted in an enclosure and in particular to a cooling system employing a heat pipe to conduct heat to a heat sink outside the enclosure.
2. Description of Related Art
When electronic components are installed in an enclosure, it is often necessary to remove the heat those components generate from the enclosure so that the components remain sufficiently cool to operate properly. The most common way to remove heat from an electronic component is through a metallic heat sink attached to the component. Heat travels by conduction from the component to the heat sink's fins which then radiate the heat into the surrounding air within the enclosure. A fan installed on an enclosure wall forces hot air away from the heat sink fins and out of the enclosure. However when a large number of electronic components are densely packed into a small enclosure, as for example the chassis of a notebook or laptop computer, it is difficult to provide enough space between the components for heat sinks without obstructing pathways for cooling air flow.
One way to remove heat from an enclosure without relying on cooling air is use a heat pipe. U.S. Pat. No. 5,579,830, issued Nov. 28, 1995 to Giammaruti, discloses the use of a large tubular heat pipe passing through the wall of an equipment enclosure. One end of the heat pipe extends into the enclosure and absorbs heat generated therein. The heat pipe conducts that heat to an opposite end extending outside of the enclosure. The external end of the heat pipe acts as a heat sink radiating the heat into the surrounding air. While this system does not require heat sinks or cooling air flow within the enclosure, it may be difficult to find clearance for a large, tubular heat pipe within a tightly packed enclosure. Also a large heat sink extending out of the enclosure is vulnerable to damage, particularly if that enclosure is the chassis of a portable notebook or laptop computer.
U.S. Pat. No. 5,642,775, issued Feb. 16, 1996 to Akachi, discloses a thin flat plate heat pipe formed from a thin plate having a set of small channels ("capillary tunnels") therein partially filled with fluid. When one end of the plate is heated, the fluid in each channel at the warm end of the heat pipe evaporates. The fluid vapor migrates to the cool end of each the channel where it condenses and flows back toward the warm end of the channel. The circulating vapor and fluid in each channel conveys heat from the warm end of the channel to the cool end. Akachi's flat plate heat pipe could fit into tight spaces in an equipment enclosure, for example between printed circuit cards installed in a motherboard. However Akachi does not indicate how such a heat pipe could be adapted for removing heat from an equipment enclosure. Akachi teaches using an extrusion method for producing a heat pipe plate with capillary channels formed therein. However it may be difficult to provide a plate with a large number of small tightly packed capillary channels by extrusion.
U.S. Pat. No. 5,697,428 issued Dec. 16, 1997 to Akachi discloses forming channels in a flat plate heat pipe, apparently by cutting them into the plate. However such a method is slow and expensive. Also, channel walls formed by cutting can be rough and less conducive to fluid flow than channel walls formed by extrusion.
What is needed is an efficient, inexpensive, easy to manufacture and install cooling system for removing heat from a tightly packed enclosure that does not rely on cooling air flow within the enclosure, does not require substantial space within the enclosure, and does not require bulky or unwieldy structures outside the enclosure.